1. Field of the Invention
The present invention relates to snow surface slider mounting systems for structural sled runners of snow travel vehicles such as dog sleds, and particularly to a system and method for quickly and replaceably securing surface sliders to a structural sled runner.
2. Description of the Prior Art
It is quite common to attach low friction or wear resistant snow sliding surface runners to the bottom of sled runners or skiis on snow travel vehicles such as dog sleds or sleighs, or to landing skiis on airplanes. A number of plastics are good, general purpose, low friction bearing materials, but sliding on snow is a special situation. In practice, only two types of plastics are now commonly used with good results: ethylene and tetrafluorethylene polymers. U.S. Pat. No. 2,938,879, granted to Mock et al. on May 31, 1960, which is hereby incorporated by reference, further discusses polyethylene compounds and compositions having low friction coefficients. Such slider material compounds often include surface active agents or slip additives to further increase snow sliding performance.
There is no single optimum slider material for all snow trail conditions, however. The sliding performance of a surface slider on snow is a function of a number of variables, including snow conditions, speed, loading and slider geometry and composition. At times, the snow surface slider must also operate under conditions of severe abrasion as on sections of trail where no snow is present. Certain materials wear or otherwise perform better under such circumstances. For these reasons, it is desirable to provide means to interchange surface sliders of different material composition and geometry not only as they become worn, but sometimes more frequently to insure optimum performance under the prevailing trail conditions.
Prior surface sliders have been secured to sled runners in a variety of ways. One common method is to adhesively bond the surface slider to the sled runner. Unfortunately, many materials which perform well sliding on snow are difficult to bond adhesively. For example, surface sliders of typical low friction polymers such as ethylene or tetrafluorethylene or other fluoro carbons would be desirable because of their superior sliding performance with respect to snow. Because of their low surface energy, however, such materials require special preparation of the surface of the side of the slider to be adhered to the sled runner. Etching, oxidation or abrasive treatment has been used to permit the use of conventional adhesives. An additional difficulty has been encountered in the use of adhesives in that they must be applied under controlled conditions of temperature and/or pressure until the adhesive is partially cured. This makes the changing of surface sliders on a sled runner in the uncontrolled conditions of the field quite difficult, if not impossible.
Another method previously employed to secure surface sliders to sled runners is to provide a mating dovetail arrangement between portions of the surface slider and sled runner. This means of attachment is shown in the following United States patents which are hereby incorporated by reference:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 488,266 Jordan 12/20/1892 375,214 Stevens 12/20/1887 323,234 Thompson 07/28/1885 286,371 Baldwin 10/09/1883 223,062 Nichols 12/30/1879 ______________________________________
The surface sliders of these patents are either permanently affixed to the sled runner or are quite difficult and cumbersome to remove and/or replace. In the device of the Baldwin patent, for example, the surface slider is held to the sled runner by a plurality of countersunk screws extending upwardly through the slider into the sled runner along the entire length thereof. To replace the surface slider of Baldwin (if that is possible) would necessitate the removal of each screw, a time consuming and laborious task in the field. In addition, once a replacement surface slider has been fitted onto the sled runner, each screw must be inserted again, and such fasteners create interference with the snow sliding surface of the surface slider. Another disadvantage from using fasteners such as those shown in Baldwin is that the surface slider material must be adequately thick to permit the countersinking of the screw heads and to prevent lifting or buckling between fasteners, which necessarily depends upon the spacing of the fasteners and the rigidity of the surface slider material.
Other attempts to fasten surface sliders to the bottom of sled runners or skiis are shown in the following United States patents which are hereby incorporated by reference:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 2,016,187 Vincent 10/01/35 3,120,963 Seckel 02/11/64 3,751,057 Matthiessen 08/07/73 ______________________________________
The surface slider attachment schemes shown in these patents are not longitudinal dovetail arrangements, but do show surface sliders configured in lateral cross-section to conform to the shape of a sled ski and means for securing these surface sliders with respect thereto. The surface sliders shown in these patents are not easily removable or easily changed in the field, however.
The use of tetrafluorethylene and ethylene polymer compounds as materials for snow surface sliders in prior art surface slider application schemes is subject to some or all of the following limitations: (1) high material cost (the slider must be relatively thick to attain the necessary rigidity to avoid buckling); (2) limited availabity; (3) difficult, costly and time consuming to adhere to a sled runner; and (4) difficult and time consuming to attach with mechanical fasteners, with impaired performance by the exposure of mechanical fasteners at the snow sliding surface (e.g., screw, bolt or rivet heads).
The snow slider replacement method of the present invention and the slider securing system for performing the same overcomes the disadvantages of prior art surface slider application schemes. With the present invention, a surface slider of the most desirable material can be provided in the most desirable slider configuration without concern for buckling of the surface slider during use or when worn. Such a surface slider can be quickly replaced with the surface slider replacement system of the present invention and is mounted with respect to the sled runner in such a manner that the snow sliding surface has no friction reducing fasteners or protrusions extending therefrom. The system and method of snow surface slider replacement of the present invention is easily used in the field, where conditions such as temperature and other weather conditions present important limiting factors in the fastening of a surface slider to a sled runner. In addition, the present invention allows the use of thinner surface sliders of certain desired materials than was previously possible with the prior art surface slider attachment schemes.